1. Field of the Invention
The present invention relates to an image processing apparatus and an X-ray diagnostic apparatus for imaging perfusion in myocardium.
2. Description of the Related Art
For example, blood supply to (or perfusion of blood in) myocardium is indispensable for a heart to beat. In conventional angiographic diagnoses, only blood vessels are observed while myocardium is not often observed. Owing to recent progress in imaging technology, X-ray images have become able to be obtained with high time resolution and with high image quality, and concrete methods for measuring myocardial perfusion have hence been proposed. For example, Jpn. Pat. Appln. KOKAI Publication No. 2008-136800 has proposed a method for creating a perfusion image from a relationship between a reference time density curve, which concerns a reference region set as a blood supply region for myocardium, and time density curves, which concern plural local region set in a myocardial region.
Consideration will now be taken into a case that a constricting lesion exists in a blood vessel. Since the constricting lesion hinders blood flow, periphery of the blood vessel where a stenosis occurs requires a longer time until a contrast medium reaches, or a sufficient amount of blood is not supplied, in comparison with a case of no stricture occurring. For example, a first peripheral region of a first stenosis is supposed to be supplied with a sufficient amount of blood after a long time. A second peripheral region of a second stenosis is supposed to be supplied with an insufficient amount of blood after a long time. In this case, a time density curve at the first region has a similar shape and a different time phase to those of a time density curve (TDC) at a normal region. However, a time density curve at the second region has a different shape and a different time phase to those at a normal region. Therefore, perfusion images indicative of risk are obtained from both regions. Consequently, there is a problem that whether or not blood is supplied to myocardium in these regions cannot be distinguished although blood can be found to not be supplied at adequate timing to myocardium in the regions.